Ethanol has a variety of uses, including as an industrial chemical and solvent, fuel additive, and straight liquid fuel. Ethanol is a clean burning fuel that can be produced from renewable sources such as crops (e.g., corn, and sugar cane), wood waste, agricultural waste, or other biomass. Ethanol not only reduces air emissions, but it also improves engine performance. Also, as a renewable fuel, ethanol reduces the United States' dependence on foreign fossil fuels. Recently, ethanol production in the United States has grown from 175 million gallons in 1980 to 3.4 billion gallons in 2004. There are currently 101 ethanol production facilities on-line in the U.S., and 30 more are under construction. Therefore, the production of ethanol in coming years is expected to increase.
The majority of ethanol made in the U.S. is derived from corn; however, ethanol can also be produced from other crops high in starches and sugars, such as grain sorghum, wheat, barley, potatoes, sugar cane, or sugar beets. The production of ethanol starts with breaking down the complex sugars (e.g., amylose, cellulose) found in these plants into simpler fermentable sugars (e.g., dextrose). This first step can be accomplished using enzymes, acid, water, and/or heat. Once the simpler sugars are obtained, yeast or other fermenting microorganisms are added to covert the sugar to ethanol. The ethanol is then removed from the fermentation by distillation. Water may be removed from the ethanol by dehydration, and the ethanol may be denatured to make it unfit for human consumption by adding a small amount of gasoline or other alcohol (e.g., methanol).
The production of ethanol as a fuel supplement has many benefits including boosting the economy, creating jobs, benefiting agriculture, aiding rural economic development, providing energy security and independence, reducing greenhouse gas emissions, and reducing emissions of other pollutants including carbon monoxide, particulate matter, oxides of nitrogen, and other ozone-forming pollutants.
Joseph DePardo in an article entitled “Outlook for Biomass Ethanol Production and Demand” (www.eai.doe.gov/oiaf/analysispaper/biomass.html) has said that the production of ethanol from corn is a mature technology that is not likely to see significant reductions in production costs. He hypothesizes that the ability to produce ethanol from other low cost biomass will be important to making ethanol competitive as a fuel additive. Therefore, a need remains for improving the production of ethanol from crops as well as other biomass including “non-virgin” biomass such as municipal solid waste.